Lead-acid batteries are widely used due to their reliability and relatively low cost. For example, most automobiles include a lead-acid battery for providing power for engine starting and other uses. Although there are many types of lead-acid batteries, their general construction includes “positive” and “negative” lead or lead alloy plates in contact with an acid electrolyte, typically dilute sulfuric acid. During discharge, electricity is produced from the reaction of the sulfuric acid and the electrode plates, the electrolyte losing dissolved sulfuric acid and lead sulfate being created in the plates. The process is reversible, so that the battery can be recharged.
It is necessary that the positive and negative plates remain electrically isolated. To this end, “separators” are used to maintain the spacing between the plates while allowing the plates to be very closely spaced. In some batteries, thin rubber sheets are used as separators, electrically isolating the plates but allowing ion exchange between the electrolyte and the plates for charging and discharging of the battery.
One particular type of lead-acid battery is the absorbed glass mat (AGM) battery. In this type of battery, a fibrous glass mat is used in the separator between the plates, and also holds the electrolyte in place between the plates by absorbing the electrolyte into the mat. This reduces the amount of electrolyte necessary, since the interior of the battery need not be completely flooded with electrolyte, and has other advantages.
Nonwoven mats are used for other purposes in lead-acid batteries as well. Improved glass mat materials are desired.